1. Field of the Invention
The present invention relates to a sheet for protecting a paint film from damage such as scratches and dirt.
2. Description of the Related Art
Techniques are known for adhering a protective sheet to a paint film disposed on an article (e.g., painted automobiles and automotive components, building materials, sheet metal such as sheet steel and shaped articles thereof) in order to prevent damage to the paint film surface, for example, during transporting, storing, curing or constructing the article. Paint film-protecting sheets used for such a purpose generally have a pressure-sensitive adhesive (PSA) layer on one side of a sheet-shaped substrate made of resin, and are constructed to perform its protective purpose by bonding the protecting sheet to the adherend surface (the paint film to be protected) via the PSA layer. Examples of background art documents relating to paint film-protecting sheets include Japanese Patent Nos. 2832565 (U.S. Pat. No. 5,747,132), 2,832,579 and 2,832,589 (U.S. Pat. No. 5,601,917).
It is desirable for paint film-protecting sheets to have the property that no adhesive residues (typically some of the PSA forming the PSA layer) from the sheet remain on the surface of the paint film (a phenomenon known as “adhesive transfer”) after the paint film-protecting sheet has been stripped (removed) from the surface of a paint film, when it is no longer needed for protective purposes. Known approaches for preventing adhesive transfer include disposing a prescribed anchoring agent between the substrate and the PSA. For instance, in the working examples disclosed in Japanese Patent Application Publication No. 2005-213280, an anchoring agent layer (e.g., ethylene-vinyl acetate copolymer or ethylene-methacrylic acid copolymer) is provided between a polypropylene film serving as the substrate and an acrylic-based PSA, and the effects of such a layer were assessed.